Power hammer



Aug. 22, 1939. J; HOLLOWAY 2,170,757

POWER HAMMER Filed July 28, 1936 4 Sheets-Sheet 1 Aug. 22, 1939. J.HOLLOWAY POWER HAMMER Filed July 28, 1936 4 Sheets-Sheet 3 Aug. 22,1939.

J. HOLLOWAY POWER HAMMER Filed July 2a, 1936 4 Sheets-sheaf: 4

Patented Aug. 22, 1939 UNITE-i) S'EATES POWER HAMMER John Holloway,Burnham, England, assignor to Holloway Patents Limited, Slough, Bucks,

England .Application July 28, 1936, Serial No. 93,075 ImGreat BritainJuly 30, 1935 21 Claims.

This invention relates to power hammers or like machines which aremechanically operated to perform'work by delivering blows as from ahammer such for example as pile drivers, rammers, stamping machines,forging presses and heading machines and generally to mechanism fordelivering impulsive forces hereinafter referred. to as power hammers.

The primary object of the invention is to provide new or improved meansfor operating such machines which will render the machines substantiallynon-reactive in 'use, and allowing the machines to be constructed inlight metals such as aluminium alloy. This combination is of particularadvantage in the case of handoperated pneumatic tools suchas roadbreaking drills, hand riveting machines and the like, because of theease with which they can be manipulated and the resulting freedom fromvibration and recoil.

Another object of the invention is to compress an elastic medium betweentwo bodies or pistons which are mechanically interconnected by meansadapted to bring the bodies or pistonsinto a substantially, butpreferably not completely, balanced condition, the said means beingemployed to balance the forces and/or the stored energy and, operatingin conjunction with other mechanism hereinafter described, to permit thestored energy to be used for performing the work of hammering or thelike in the machine wherein the energyis stored whereby the aforesaidnonreactive property is secured.

The invention consists of a power hammer or the like comprising twomoving bodies or pistons connected through means allowing them to movein the same direction at differential speeds, the arrangement being suchthat with the fastermoving body or pistonovertaking the slower-movingbody or piston work is performed upon an elastic medium between the twomoving bodies or pistons to store energy in the medium which at apredetermined point in the stroke of the moving bodies or pistons isutilized to return or to assist in returning the moving bodies orpistons at a greatly accelerated speed to their original positionsresulting in the delivery of an impulsive force.

It will be understood that the mechanism may be operated by manual or bymotive power and also that'the moving bodies may be fashioned or shapedas desired. or may be attached to tools or the like, according to thenature of thework and the use for which the mechanism is to be employed.

Several embodiments of the invention will now be more particularlydescribed, by way of example, with reference tothe accompanying drawingsin which:

Figure 1 is a vertical section through a power hammer made according tothe invention and .5. showing the same applied to a pneumaticallyoperated road-breaking drill,

Figure 2 is a cross section through the machine casing on the line Z-2of Figure 1 on an enlarged scale showing the arrangement of the inletand exhaust passages therein,

Figure 3 is a cross section on the line 3-3 of Figure 1 on an enlargedscale showing the disposition of the exhaust port,

Figure 4 is a diagrammatic view of a hand or power operated hammer inwhich the moving bodies or pistons are reciprocated through the meansconnecting them together,

Figure 5 is a vertical section through a hand operated riveting hammerembodying the invention, and

Figures 6 to 9 are detail views on an enlarged scale of parts of thehammer shown in Figure 5.

Referring to Figures 1 to 3, the road-breaking drill shown thereincomprises a casing 6 including a handle 6d and the moving bodies consistof pistons I and 9 movable in a cylinder 2| which is preferably formedwith a liner Zld provided in the casing 6. A compression coil spring 8is located between the pistons I and 9 and in the embodiment shownconstitutes part of the elastic medium in which energy is stored, theother part being the air between the two pistons. It will be understoodthat alternatively any suitable compressible fluid may be employed asthe elastic medium between the two pistons with or without a spring suchas 8, as desired. The lower part of the piston 9 is formed with areduced skirt at 9d to allow it to telescope into the skirt Id of thelower piston I to sealthe space wherein the compression spring 8 iscontained from the relatively small annular space 30d between the pistonskirts and the wall of the cylinder 2|. A bell crank lever Ill isfulcrumed at H on the casing 6 and to angularly spaced points l2 and [3of the bell crank lever, links I4 and I5 are pivotally connected, beingattached at their opposite ends to gudgeon pins l6 and I! respectivelyof the pistons 1 and 9. The bell crank lever Ill and links M and I5 arepreferably duplicated so that they 50 are symmetrical with the verticalcentre line of the casing 6 to ensure smooth working, the ends of thegudgeon pins l6 and I! projecting through slots [8 and I9 respectivelyin the casing and having a link M or IE connected thereto respec- 55bell cranklever I0 and links I4 and. I5 are as shown in Figure l, thelinks being of such length that the'spring 8 is as nearly as desiredrelieved of compression. It will be noted that with the pistons in thepositions shown, the pivot I3 lies nearly vertically below the fulcrumII while a line running through the pivot I2 and fulcrum I I makes anangle of about 40 below a horizontal 'line drawn through the fulcrum.Now the bell crank lever I9 may be considered as two rigidlyconnected'levers or arms the ends of which are defined by the points IIand I3 and II and I2 respectively the former constituting. what may betermed a balance arm due to its connection to the. balance piston 9andthe latter constituting a power arm due to its connection to thehammer head or power piston I. It will be seen on reference to Figure 1'that if the bell crank lever Ill be rotatedupwards. through an arc of,say, 60 the power arm II, I2 of the bell crank will move the piston I inavertical direction a distance almost equal to the radius of the pivotI2 from the fulcrum I I whereas the balance arm I I v I3 due to the samerotation of the bell crank will move the piston '9 in a verticaldirection a distance only approximately half that covered by the pistonI, and the difference between the strokes of the two pistons representsthe amount the spring 8 is compressed.

' anced. It will be seen that when the bell crank is moved to a.position where the power and balance arms are not quite at equal anglesto the horizontal, the leverages are unequal and out of balance, so thatwhen the balance arm is moved back towards the initial position shown inFigure 1 its leverage about the fulcrum II rapidly decreases while theleverage of the power arm tends to increase, with the result that thepiston I descends with the force of the energy stored in the spring 8.

When compressed air is used for power, the operation of the machine isas follows:-

Compressed air enters the drill casing 6 by the connection 20, passesthrough a valve 22 when the latter is depressed by the handle 23 underthe control of the operative, and passes thence by a 'port 24 into anair chamber 25 running substantially the whole length of the casing ii,as shown. From the lower end of the air chamber 25 the compressed air isled through a port 25 to the underside of a control valve 2! working ina control valve chamber 28 carried by the casing 6. The pressure of thecompressed air lifts the control valve 2! to uncover an inlet port 29through which the air passes to the cylinder 2! beneath the piston Iwhich rises against the resistance of the spring 8 and causes the piston9 to travel in the same upward direction until the lower reduced portion9d of the latter uncovers an air port 39 in the cylinder 2|. Compressedair then passes from the air chamber 25 through the air port 39, intothe annular space 39d between the piston skirts and the wall of thecylinder 2! (which space has been closed by the skirt id telescopingover the skirt 9d and is sealed off from the space containing the spring8 whereby the consumption of compressed air is economized), to a port 3Ithrough which it passes to a conduit 32 to the top of a piston 33 in thecontrol valve chamber 28. The piston 33 has a stem 33a contacting withthe top of the control valve 21 and held thereto by the pressure of acoil spring 34 so that the piston 33 and control valve 21 always move asa unit. The piston 33 is of larger cross-sectional area than the controlvalve 21 whereby the admission of compressed air through the conduit 32mentioned above depresses the piston and the control valve 21 to closethe latter onto its lower seating thereby closing the port 26, to out01f the compressed air from the cylinder 2| beneath the piston T, and atthe same time opening a port 35 allowing the air in the cylinder 2! tobe exhausted therethrough to an exhaust port 36.

and thence to atmosphere. At the same time, the pressure of thecompressed air filling the space 38d between the pistons I and 9, due tothe out of balance position of these latter, is added to' the energystored in the spring 8 and causes both pistons to descend, the lowerpiston I striking the tool 31 which may be a pick, as shown, or a chiselor rammer head and which projects into the bottom of the cylinder 2 I.As the piston I movesaway from the piston 9 the space 38d is re-openedto the space containing the spring 8 and the compressed air exhauststhereinto from the space 30d and so to atmosphere by the slot I8. Due tothe fact that the resistance to the movement of the piston I is efiectedby the piston 9 instead of by a stationary element such as a cylindercover, there is no force exerted on the cylinder or casing to causerecoil such as is found on pneumatic hammers of the ordinary type andthe casing 6 therefore remains substantially non-reactive. It will beseen that as the port 35 remains open during the descent of the pistonsI and 9, there is no resistance to impede the. accelerated speed atwhich the latter fall. At the moment when the blow is struck, that. iswhen both pistons are at the bottom of their strokes, ports 53 in thepiston 9 come opposite the port 3| and thereby compressed air escapesfrom the top of the piston 33 to atmosphere. The ports 38 in the'piston9 are positioned opposite the port 3| (Figure 2) sothat they never opento the port 38, carrying compressed air from the air chamber 25. Thepressure being released from the top of the piston 33, the compressedair forces open the control valve 21 thereby closing the port 35 leadingto the exhaust port 36 and admitting compressed air into the bottom ofthe cylinder 2I beneath the piston I and the cycle of operations is thenrepeated.

When the machine described is to be employed as a rammer, for sloweroperation of the rammer head which replaces the pick 31, the valve 22 isnot opened fully, thereby limiting the rate at which the compressed airpasses into the cylinder ZI from the air inlet chamber 25, so that thespeed of the pistons 1 and 9 and of the actuation of the rammer head maybe regulated.

Figure 4 shows a hammer provided with operating mechanism according tothe invention in which the actuation of the moving bodies or pistons la,9a is effected from the fulcrum Ila of the lever Wu. The lattercomprises a power arm iio;,l2a and a balance arm Ha,-=-l3a as before andthe machine is operated by applying the effort to the lever Eta insteadof to the lower moving body or piston as in the embodiment previouslydescribed. The means by which the effort is applied to the lever Illaconsist of a swivelling member or ratchet arm 39 pivotally mounted onthe fulcrum Ha of the lever ma and having a pawl it one end 490? ofwhich is shaped to engage in a notch or step led out in the hub of thelever lea. The other end of the pawl 4i! comprises a face Me which isapproximately at right angles to the operative face of the end 40d.Preferably the oscillatory lever lilo is duplicated as before, as isalso the pawl lll so that a pawl is carried at-each side of the ratchetarm 39 upon a fulcrum M, the pawls being connected together by a pin t2against which a flat spring 43 bears to ensure that the pawls act uponthe hub of the lever ltd, in unison. The ratchet arm 39 with the p awls6 and spring 43 is similar in operation to an ordinary ratchet exceptthat the engage with the same notch or step ltd on the lever its at eachstroke of the ratchet arm 3e and lever tea, but a series of notches orsteps i ay be employed in order to provide for variation the length ofstroke of the moving bodies or pistons. The latter in the embodimentshown in Figure 4. consists of lower and upper blocks la to slidablycarried in vertical channel memb. s 44 provided with clamping means 45at their upper and lower ends. The blocks to and 911 have a compressionsprin g Ba. located between them and are connected to the points I20.and 53a of the oscillatory lever lilaby links Ma and i5a the same manneras are the pistons "l and 9 to lever it in the embodiment previouslydescribed. To throw the pawls 40 out of action when the desired point inthe stroke of the blocks and is reached to leave the lower block la todescend due to the energy stored in the spring Sic, aprojection 46 isadjustably carried on the frame of the machine, being so arranged as tomake contact with the faces Me of the nawls when the ratchet arm 39 ismoved downwards to cause the pawls to turn about the fulc. m ii in aclockwise direction to take the ends clear of the hub of the oscillatorylever Illa.

The ratchet arm may be operated by a hand lever l"! or by a prime mover48 through a connecting rod 49.

In cases where a portable unit is desired the in cancer frame may beattached to a base fitted Iv wheels, rollers or other means forlocomotion. Likewise when the hammer is required for use on such workfor instance as pile drivor metal stamping, the power unit 48 may bemounted on or near the frame of the machine and connected to theoscillatory bell crank [0a by gearing or other suitable means.

Figure 5 shows a hammer intended for use where a succession of lighthammer blows of a specified weight is required, such as in the headingof small rivets in somewhat delicate metal work. such as for example themetal bodies of aircraft. The hammer shown is hand operated, ti pistonsor blocks lb and 9b being actuated by a finger grip 50 located withinthe handle 5! of the hammer. The pistons or sliding blocks and 8b spring8b, bell crank I079. links Mb and liib and tool 3119 are similar to thecorresponding parts of the embodiments already described. The fingergrip 50 is swivelly connected to an outer piston 52 slidably mounted inthe upper end of the hammer casing 6b, and an inner piston 53, overwhich the outer piston 52 is slidable, has a rod 54 rigidly connectedthereto. The rod 54 passes loosely through the upper piston or block 913and is connected at its lower end to the lower piston or block lb. Theouter piston 52 carries a substantially radially projecting stop pin 55(Figures 5, 7 and 9) one end of which projects inwardly to engage with anotch 55 in the inner piston 53 to couple the latter to the outer piston52 while the other end projects outwardly to engage in a groove GI inthe inner surface of the casing Eb. The groove 6! is mainly vertical butits upper end E52 curves in a counter-clockwise direction as shown inFigure 8. With the parts in the position shown in Figure 5 the operationof drawing the finger grip 5i) upwards towards the handle 5i causesupward movement of the pistons or blocks lb and 9b in the casing 6btowards a point of balance as described with reference to Figure 1.Before this point is reached however the inner piston 53 is uncoupledfrom the outer piston 52 due to the outer end of the stop pin 55 passinginto the curved part 62 of the groove 5! whereby the piston 52 isrotated in a counter-clockwise direction resulting in the inner end ofthe stop pin 55 being removed from the notch 56 into a position oppositea vertical slot 58 in the inner piston 53. This uncoupling of thepistons 52 and 53 allows the inner piston with the rod 54 and pistons orblocks lb and 9b to descend under the influence of the compressed spring8b, the lower piston or block 9b striking the riveting head 37b todeliver a blow.

Due to the non-reactive property of the riveting hammer described and tothe definite and constant weight of blow delivered at each strokeirrespective of the manner of operation of the finger grip 50, it willbe appreciated that the hammer is more efiicient in use than theriveting hammers at present in use. Furthermore with the bell cranklever and linkage construction described, the leverage is increased asthe balance arm of the bell crank lever approaches the original positionof the power arm and the upward pull exerted on the spring 82) by theupper block ab begins to approximate to the pull exerted on the lowerblock lb by the operative so that as the point of trip is approached theoperative is exerting little or no efiort on the finger grip 5B. Thispoint is of importance as it enables the hammer to be used for work uponwhich it is impossible to use known constructions of riveting hammers.

If desired a safety device may be fitted to the machine, whetherconstructed as a riveting hammer or as a stamping or embossing machine,to prevent the piston or block la falling and delivering a blow beforethe piece on which work, such as stamping and embossing is to be done,has been properly set in position. In cases of this nature the bellcrank Gila may be moved through the required are to bring the balancepiston or block 9a and the lower piston or block la. into completeequilibrium, whilethe energy in the compressible medium remains stored.This may be achieved as shown in Figure 4% by adjusting the projection 6to the position shown at 46a. so that the system is not tripped untilreaches the point of equilibrium. It has already been shown that thiscircumstance there will be no movement of the piston or block 'ia and itwill be apparent that a further operation will be necessary to put themechanism out of balance and allow the stored energy to be released,bringing down the piston or block 10.. The safety device may consist ofa small lever 63 or similar attachment which may be pivoted to thecasing 6d at 63a. To put the mechanism out of balance the lever 63 hasto be moved by the machine operative about its pivot 630. so that aprojection 63b strikes the top of the balance piston or block 9a. Ifdesired however, a safety catch may be fitted in a convenient positionas an alternative to bringing the mechanism to a point of balance andthen moving it therefrom. This may be fasmoned in the form of spring orweight loaded pawl it the nose 64a of which automatically snaps intoplace at the desired point of the stroke behind the piston or block 9aand prevents the latter from descending until the mechanism is trippedby the operative when the blow is required to be struck. Tripping may beeffected by grasping the knob 6411 and withdrawing the plunger nose fromthe path of the block 9a. The plunger may be locked in an inoperativeposition by a pin and. slot device 660. This arrangement applies topower operated machines as well as to those operated by hand.

When the mechanism is used on stamping or embossing machines, where itis necessary for the stamp and die component to be guided in perfectalignment, the members effecting this guiding may be made integral withthe frame or body of the machine.

What I claim and desire to secure by Letters Patent is: a

1. In 'a power hammer the combination of a support, two bodies slidableon said'support, a lever mechanism to connect said bodies together andallow them to slide on said support in the I same direction atdifierential speeds, an elastic medium between said bodies, means tocause said bodies to slide on said support to compress. said elasticmedium between the faster and the slower moving body, and meansoperative at a predetermined point in the stroke of the moving bodies torelease the energy stored in said elastic medium to accelerate thereturn of said bodies to their original positions to cause the deliveryof an impulsive force by said faster moving body.

2. In a power hammer the combination of a support, two bodies slidableon said support, a lever and link mechanism to connect said bodiestogether and to allow them to slide on said support in the samedirection at differential speeds, an elastic medium between said bodies,means to cause said bodies to slide on said support to compress saidelastic medium between the faster and the slower moving body, and meansoperative at a predetermined point in the stroke of the moving bodies torelease the energy stored in said elastic medium to accelerate thereturn of said bodies to their original positions to cause the deliveryof an impulsive force by said faster moving body.

3. In a power hammer the combination of a support, two bodies slidableon said support, a lever pivoted on said support, means to couple saidbodies to said lever at different points giving said bodies adifferential leverage about said pivot whereby said bodies are allowedto slide on said support in the same direction at differential speeds,an elastic medium between said bodies, means to cause said bodies toslide on said support to compress said elastic medium between the fasterand the slower moving body, and

means operative at a predetermined point in the stroke of the movingbodies to release the energy stored in said elastic medium to acceleratethe return of said bodies to their original positions to cause thedelivery of an impulsive force by said faster moving body.

4. In a power hammer the combination of a support, twobodies slidable onsaid support, a lever pivoted on said support and having said bodiesconnected thereto at different points giving said bodies a differentialleverage about said pivot whereby said bodies are allowed to slide onsaid support in the same direction at differential speeds, an elasticmedium between said bodies, means, to cause said bodies to slide on saidsupport to compress said elastic medium between the faster and theslower moving body, and means operative at a predetermined point in thestroke of the moving bodies to release the energy stored in said elasticmedium to accelerate the return of said bodies to their originalpositions to cause the delivery of an impulsive force by said fastermoving body.

5. In a power hammer the combination of a support, two bodies slidableon said support, a rockable member including two rigidly connectedangularly disposed arms having a common fulcrum and operating on saidbodies to allow them to slide on said support in the same direction atdifierential speeds during each stroke, said arms being located to causethe faster moving body to exert a greater leverage about the fulcrumthan the slower moving body at the commencement of a stroke and theleverage of said faster moving body decreasing rapidly and the leverageof said slower moving body increasing slowly during the stroke until atthe end of the stroke the leverages are almost equal, an elastic mediumbetween said bodies, means to cause said bodies to slide on said supportto'compress said elastic medium between said faster and slower movingbodies, and means operative when said leverages are almost equal torelease the energy stored in said elastic medium to accelerate thereturn of said bodies to their original positions to cause the deliveryof an impulsive force by said faster movingbody.

6. In a power hammer the combination of a support, two bodies slidableon said support, a linkage connecting said bodies together and to allowthem to slide on said support in the same direction at differentialspeeds whereby one body moves faster than the other, an elastic mediumbetween said bodies, means to apply a driving force directly to saidfaster moving body to cause said bodies to slide on said support tocompress said elastic medium between the faster and the slower movingbody, and means operative at a predetermined point in the stroke of themoving bodies to release the energy stored in said elastic medium toaccelerate the return of said bodies to their original positions tocause the delivery of an impulsive force by said faster moving body.

'7. In a power hammer the combination of a support, two bodies slidableon said support, a rockable member including two rigidly connectedangularly disposed arms having a common fulcrum and operating on saidbodies to allow them to slide on said support in the same direction atdifferential speeds during each stroke whereby one body moves fasterthan the other, said arms being located to cause the faster moving bodyto exert a greater leverage about the fulcrum than the slower movingbody at the commencement of a stroke and the leverage of said fastermoving body decreasing rapidly and the leverage of said slower movingbody increasing slowly during the stroke until at the end of the strokethe leverages are about equal, an elastic medium between saidbodies, aratchet arm having a connection with said rockable member. means toapply a driving force to said ratchet arm to rock said rockable memberabout its fulcrum to cause said bodies to slide on said support tocompress said elastic medium between the faster and the slower movingbody, and means operative at a predetermined point in the stroke of themoving bodies to release the energy stored in said elastic medium toaccelerate the return of said bodies to their original positions tocause the delivery of an impulsive force by said faster moving body.

8. In 'a power hammer the combination of a support, two bodiesreciprocable on said support, a linkage connecting said bodies togetherand cause them to slide on said support in the same direction atdifierential speeds during each stroke, an elastic medium between saidbodies, said elastic medium being compressed between the faster movingbody and the slower moving body, and means for tripping said linkagewhen a point of leverage in which the bodies pull equally in oppositedirections on said linkage is almost reached to release the energystored in said elastic medium to accelerate the return of said fastermoving body to its original position to deliver an impulsive force.

9. In a power hammer the combination of a cylinder, a power piston and abalance piston slidable in said cylinder, a linkage connecting saidpistons together and allow said power piston to slide in said cylinderin the same direction as said balance piston at a higher speed than thelatter during each stroke, an elastic medium between said pistons, drivemeans to cause said pistons to reciprocate in said cylinder to compresssaid elastic medium between said power piston and said balance pistonagainst the resistance of said elastic medium, and means to trip saidlinkage at a predetermined point in the stroke to permit the energystored in said elastic medium to be utilised to accelerate said powerpiston to its original position to deliver an impulsive force, thereaction to the force exerted being absorbed by said balance pistonthereby rendering the hammer substantially nonreactive,

10. In a power hammer the combination of a cylinder, at power piston anda balance piston slidable in said cylinder, a linkage connecting 'saidpistons together and allow said balance piston to slide in said cylinderin the same direction as said power piston at a lower speed than thelatter, a spring located between said power and balance pistons, and acontrol valve controlling the introduction of fluid under pressure intosaid cylinder between a closed end thereof and said power piston, thepistons being moved by said fluid to compress said spring until saidbalance piston uncovers a port allowing fluid under pressure to entersaid cylinder between said. pistons and pass to said control valve whichit actuates to cut off the supply of fluid to the space between saidclosed end of the cylinder and said power piston and simultaneously toopen said space to exhaust, whereby said pistons are accelerated totheir original positions where said power piston delivers an impulsiveforce under the influence of the pressure of said fluid admitted betweensaid pistons and. the energy stored in said spring.

11. In a power hammer according to claim the combination wherein thepistons have re duced and skirted parts allowing said pistons totelescope and seal off a space containing said spring from an annularspace formed between the wall of the cylinder, the reduced part of onepiston and the skirt of the other piston, and enables fluid underpressure to enter said annular space which is connected with a portleading to said control valve.

12. In a power hammer the combination of a support, two bodies slidableon said support, a linkage connecting said bodies together and to allowthem to slide on said support in the same direction at difierentialspeeds whereby one of said bodies moves faster than the other, anelastic medium between said bodies, and manually operable means forreciprocating said bodies on said support including a manually operableelement, means to couple one of said bodies to said manuallyoperableelement at the commencement of a stroke, and means to automaticallyuncouple said body from said manually operable element at apredetermined point in the stroke, said reciprocation compressing saidelastic medium between the faster and the slower moving body and saiduncoupling means acting to release the energy stored in said elasticmedium to accelerate the return of said bodies to their originalpositions to cause the delivery of an impulsive force by said fastermoving body.

13. In a power hammer'the combination of a support, two bodies slidableon said support, a motion-differentiating non-resilient linkage toconnect said bodies together and to allowthem to slide on said supportin the same direction at differential speeds, an elastic medium betweensaid bodies, means to cause said bodies to slide on said support tocompress said elastic medium between the faster and the slower movingbody until a point of balance is reached, and means to move saidmotion-differentiating non-resilient linkage from said point of balanceto release the energy stored in said elastic medium and accelerate thereturn of said bodies to their original positions to cause the deliveryof. an impulsive force by said faster moving body.

14. In a power hammer the combination of a support, a ram movable onsaid support, a balance body also movable on said support, a leversystem connecting said ram with said balance body so that the lattermoves in the same direction as said ram but at a lower speed and drivemeans for said ram and balance body.

15. In a power hammer the combination of a support, two bodies slidableon said support, a

bell crank lever pivoted on said support, means to couple said'bodieseach to one arm of said bell crank lever to give said bodies adifferential leverage about said pivot whereby said bodies are allowedto slide on said support in the same direction at differenetial speeds,an elastic medium between said bodies, means to cause said bodies toslide on said support to compress said elastic medium between the fasterand the slower moving body, and means operative at a predetermined pointin the stroke of the moving bodies to release the energy stored in saidelastic medium to accelerate the return of said bodies to their originalpositions to cause the delivery of an impulsive force by said fastermoving body.

16. In a power hammer the combination of a support, two bodies slidableon said support, a bell crank lever pivoted on said support and havingsaid bodies connected each to one arm of said bell crank lever to givesaid bodies a differential leverage about said pivot whereby said bodiesare allowed to slide on said support in the same direction atdifferential speeds, an elastic medium between said bodies, means tocause said bodies to slide on said support to compress said elasticmedium between the faster and the slower moving body, and meansoperative at a predetermined point in the stroke of the moving bodies torelease the energy stored in said elastic medium to accelerate thereturn of said bodies to their original positions to cause the deliveryof an impulsive force by said faster moving body.

17. In a power hammer the combination of a support, two bodies slidableon said support, a motion-differentiating non-resilient linkage toconnect said bodies together and to allow them to slide on said supportin the same direction at difierential speeds, an elastic medium betweensaid bodies, means to cause said bodies to slide on said support tocompress said elastic medium between the faster and the slower movingbody, and means operative at a predetermined point in the stroke of themoving bodies to release the energy stored in said elastic medium toaccelerate the return of said bodies to their original positions tocause the delivery of an impulsive force by said faster moving body.

18. In a power hammer the combination of a support, two non-resilientlylinked bodies reciprocable therein, drive means to cause said bodies tomove in the same direction at different speeds during each stroke sothat they alternately approach and recede from each other, an elasticmedium between said bodies which is compressed between the faster andthe slower moving body, and means operative at a predetermined point inthe stroke of the moving bodies to release the energy stored in saidelastic medium to accelerate the return of said bodies to their originalpositions to cause the delivery of an impulsive force by said fastermoving body.

19. In a power hammer the combination of a support, two bodies slidableon said support, a motion-differentiating non-resilient linkage toconnect said bodies together and to allow them to slide on said supportin the same direction at differential speeds, an elastic medium betweensaid bodies, means to apply a driving force di rectly to one of saidbodies to cause said bodies to slide on said support to compress saidelastic medium between the faster and the slower moving body, and meansoperative at a predetermined point in the stroke of the moving bodies torelease the energy stored in said elastic medium to accelerate thereturn of said bodies to their original positions to cause the deliveryof an impulsive force by said faster moving body.

20. In a power hammer the combination of a support, two bodies slidableon said support, a rockable member including two rigidly connectedangularly disposed arms having a common iulcrum and operating on saidbodies to allow them to slide on said support in the same direction atdifierential speeds during each stroke, said arms being located to causethe faster moving body to exert a greater leverage about the fulcrumthan the slower moving body at the commencement of a stroke and theleverage of said faster moving body increasing rapidly and the leverageof said slower moving body increasing slowly until a point in the strokeis reached where the leverage of said faster moving body diminisheswhile the leverage of said slower moving body continues to increaseduring the stroke until at the end of the stroke the leverages arealmost equal, an elastic medium between said bodies, means to cause saidbodies to slide on said support to compress said elastic medium betweensaid faster and slower moving bodies, and means operative when saidleverages are almost equal to release the energy stored in said elasticmedium to accelerate the return of said bodies to their originalpositions to cause the delivery of an impulsive force by said fastermoving body.

21. In a power hammer the combination of a support, two bodies slidableon said support, a rockable member including two rigidly connectedangularly disposed arms having a common fulcrum and operating on saidbodies to allow them to slide on said support in the same direction atdifferential speeds during each stroke, said arms being located to causethe faster moving body to exert a greater leverage about the fulcrumthan the slower moving body at the commencement of a stroke and theleverage of said faster moving body increasing rapidly and the leverageof said slower moving body increasing slowly until a point in the strokeis reached where the leverage of said faster moving body diminisheswhile the leverage of said slower moving body continues to increaseduring the stroke until at the end of the stroke the leverages are aboutequal, an elastic medium between said bodies, a ratchet arm having aconnection with said rockable member, means to apply a driving force tosaid ratchet arm to rock said rockable member about its fulcrum to causesaid bodies to slide on said support to compress said elastic mediumbetween the faster and the slower moving body, and means operative at apredetermined point in the stroke of the moving bodies to release theenergy stored in said elastic medium to accelerate the return of saidbodies to their original positions to cause the delivery of an impulsiveforce by said faster moving body.

JOHN HOLLOWAY.

